The present invention relates to a method and apparatus for emulsifying a pressurized multi-component liquid.
Emulsions used in industry and commerce today are usually made by violent mechanical agitation of immiscible liquids, often in discreet batches. To prevent the liquids from coalescing and losing the emulsion, several stabilizing schemes are employed. One may be surfactants added to the emulsion such as in liquid food products, water-in-fuel emulsions, or liquid paints. Another may be utilizing liquids of very high viscosity as the continuous phase. In this case although the emulsion is transient, it is stable for long periods of time. Examples of this type may be viscous latex paint emulsions, or heavy lubricating greases. Still another method may be to form the emulsion, and before it can coalesce, change the form of the emulsion from liquid to solid. Examples of this type may include dried or cured paint films, frozen or jelled food products, thermoplastic polymer emulsions, or metals alloys/emulsions.
In the case where emulsion products are marketed in batch quantities such as food products or ready-to-use paints, the products are usually made in very large batches involving mixing vessels, storage vessels, pumping and piping systems, and end container filling devices. Batch processing may be unsuitable for commercial production of large quantities of inexpensive emulsion products.
Batch production can present particular disadvantages for catalyst cured paints and other solid film-forming products in which a catalyst or reactive agent must be added to the product by the user. When the catalyst is added to the batch, the catalytic reaction begins, thus the batch must be used within a certain time period, this period usually being called the xe2x80x9cpot lifexe2x80x9d. Furthermore, the aggressiveness of the particular catalyst must be a compromise between curing time and film performance, and pot life.
Blends of gasoline-methanol, diesel-methanol, diesel-bio-diesel, diesel-water, and others are being utilized in the combustion engine and combustion energy industries as means to improve fuel source availability, or to reduce combustion emission products. These fuel blends and emulsions must be premixed and stored in tanks, and stabilizers must be used to prevent the components from separating.
Accordingly, there is a need for a continuous process that could be used to replace some large batch emulsification processes. For example, it would be desirable to have a simple process that allows for the simultaneous mixing, emulsification, and container filling of emulsion products all at the point of container filling.
There is also a need for a simple process for mixing and emulsifying a base liquid, catalyst, and other amendments including pigments at the instant of use. Meeting this need could reduce or eliminate the use of emulsion stabilizers and also allow the use of far more aggressive and faster reacting catalysts.
There is also a need for a simple and efficient process that would permit the components of fuel blends to be brought to the injection point separately, then emulsified and injected into the combustion area. Meeting this need could greatly simplify the use of such blends because the emulsion would immediately be burned, avoiding the need for added emulsion stabilizers.
The present invention addresses some of the difficulties and problems discussed above by providing an apparatus and a method for emulsifying a pressurized multi-component liquid by applying ultrasonic energy to a portion of the pressurized liquid as it is received in a chamber and passed through an orifice.
The apparatus includes a die housing which defines a chamber adapted to receive a pressurized multi-component liquid and a means for applying ultrasonic energy to a portion of the pressurized multi-component liquid. The die housing includes a chamber adapted to receive the pressurized multi-component liquid, an inlet adapted to supply the chamber with the pressurized multi-component liquid, and an exit orifice (or a plurality of exit orifices) defined by the walls of a die tip. The exit orifice is adapted to emulsify a pressurized multi-component liquid when the means for applying ultrasonic energy is excited with ultrasonic energy while the exit orifice receives pressurized multi-component liquid from the chamber and passes the liquid out of the die housing.
Generally speaking, the means for applying ultrasonic energy is located within the chamber. For example, the means for applying ultrasonic energy may be an immersed ultrasonic horn. According to the invention, the means for applying ultrasonic energy is located within the chamber in a manner such that no ultrasonic energy is applied to the die tip (i.e., the walls of the die tip defining the exit orifice). That is, the means for applying ultrasonic energy is located within the chamber in a manner such that substantially no ultrasonic energy is applied to the die tip.
In one embodiment of the present invention, the die housing may have a first end and a second end. One end of the die housing forms a die tip having walls that define an exit orifice which is adapted to receive a pressurized multi-component liquid from the chamber and pass the pressurized multi-component liquid along a first axis. The means for applying ultrasonic energy to a portion of the pressurized multi-component liquid is an ultrasonic horn having a first end and a second end. The horn is adapted, upon excitation by ultrasonic energy, to have a node and a longitudinal mechanical excitation axis. The horn is located in the second end of the die housing in a manner such that the first end of the horn is located outside of the die housing and the second end is located inside the die housing, within the chamber, and is in close proximity to the exit orifice.
The longitudinal excitation axis of the ultrasonic horn desirably will be substantially parallel with the first axis. Furthermore, the second end of the horn desirably will have a cross-sectional area approximately the same as or greater than a minimum area which encompasses all exit orifices in the die housing. Upon excitation by ultrasonic energy, the ultrasonic horn is adapted to apply ultrasonic energy to the pressurized multi-component liquid within the chamber (defined by the die housing) but not to the die tip which has walls that define the exit orifice.
The present invention contemplates the use of an ultrasonic horn having a vibrator means coupled to the first end of the horn. The vibrator means may be a piezoelectric transducer or a magnetostrictive transducer. The transducer may be coupled directly to the horn or by means of an elongated waveguide. The elongated waveguide may have any desired input:output mechanical excitation ratio, although ratios of 1:1 and 1:1.5 are typical for many applications. The ultrasonic energy typically will have a frequency of from about 15 kHz to about 500 kHz, although other frequencies are contemplated.
In an embodiment of the present invention, the ultrasonic horn may be composed of a magnetostrictive material. The horn may be surrounded by a coil (which may be immersed in the liquid) capable of inducing a signal into the magnetostrictive material causing it to vibrate at ultrasonic frequencies. In such cases, the ultrasonic horn may be simultaneously the transducer and the means for applying ultrasonic energy to the multi-component liquid.
In an aspect of the present invention, the exit orifice may have a diameter of less than about 0.1 inch (2.54 mm). For example, the exit orifice may have a diameter of from about 0.0001 to about 0.1 inch (0.00254 to 2.54 mm) As a further example, the exit orifice may have a diameter of from about 0.001 to about 0.01 inch (0.0254 to 0.254 mm).
According to the invention, the exit orifice may be a single exit orifice or a plurality of exit orifices. The exit orifice may be an exit capillary. The exit capillary may have a length to diameter ratio (L/D ratio) of ranging from about 4:1 to about 10:1. Of course, the exit capillary may have a L/D ratio of less than 4:1 or greater than 10:1.
In an embodiment of the invention, the exit orifice is self-cleaning even as it is adapted to emulsify a pressurized multi-component liquid.
The present invention encompasses a method of emulsifying a pressurized multi-component liquid. The method involves supplying a pressurized multi-component liquid to the apparatus described above, exciting the means for applying ultrasonic energy with ultrasonic energy while the exit orifice receives pressurized multi-component liquid from the chamber (without applying ultrasonic energy to the die tip), and passing the pressurized liquid out of the exit orifice in the die tip so that the multi-component liquid is emulsified.
The present invention contemplates that the method steps of exciting the means for applying ultrasonic energy with ultrasonic energy (i.e., exciting the ultrasonic horn) while the exit orifice receives pressurized liquid from the chamber and passing the liquid out of the exit orifice in the die tip may further include the step of self-cleaning the exit orifice.